UNIX — универсальная среда программирования

 PATH=/bin:/usr/bin

 case $# in
 1) ;;
 *) echo 'Usage: overwrite file' 1>&2; exit 2
 esac

 new=/tmp/overwr1.$$
 old=/tmp/overwr2.$$
 trap 'rm -f $new $old; exit 1' 1 2 15

 cat >$new # collect the input
 cp $1 $old # save original file

 trap '' 1 2 15 # we are committed; ignore signals
 cp $new $1 # overwrite the input file

 rm -f $new $old

3.8.37 overwrite3

 # overwrite: copy standard input to output after EOF
 # final version

 opath=$PATH
 PATH=/bin:/usr/bin

 case $# in
 0|1) echo 'Usage: overwrite file cmd [args]' 1>&2; exit 2
 esac

 file=$1; shift
 new=/tmp/overwr1.$$; old=/tmp/overwr2.$$
 trap 'rm -f $new $old; exit 1' 1 2 15 # clean up files

 if PATH=$opath >$new # collect input
 then
  cp $file $old # save original file
  trap '' 1 2 15 # we are committed; ignore signals
  cp $new $file
 else
  echo "overwrite: $1 failed, $file unchanged" 1>&2
  exit 1
 fi
 rm -f $new $old

3.8.38 p1.c

 /* p: print input in chunks (version 1) */

 #include <stdio.h>
 #define PAGESIZE 22
 char *progname; /* program name for error message */

 main(argc, argv)
  int argc;
  char *argv[];
 {
  int i;
  FILE *fp, *efopen;

  progname = argv[0];
  if (argc == 1)
  print(stdin, PAGESIZE);
  else
  for (i = 1; i < argc; i++) {
  fp = efopen(argv[i], "r");
  print(fp, PAGESIZE);
  fclose(fp);
  }
  exit(0);
 }

 print(fp, pagesize) /* print fp in pagesize chunks */
  FILE *fp;
  int pagesize;
 {
  static int lines = 0; /* number of lines so far */
  char buf[BUFSIZ];

  while (fgets(buf, sizeof buf, fp) != NULL)
  if (++lines < pagesize)
  fputs(buf, stdout);
  else {
  buf[strlen(buf)-1] = '\0';
  fputs(buf, stdout);
  fflush(stdout);
  ttyin;
  lines = 0;
  }
 }

 #include "ttyin1.c"
 #include "efopen.c"

3.8.39 p2.c

 /* p: print input in chunks (version 2) */

 #include <stdio.h>
 #define PAGESIZE 22

 char *progname; /* program name for error message */

 main(argc, argv)
  int argc;
  char *argv[];
 {
  FILE *fp, *efopen;
  int i, pagesize = PAGESIZE;

  progname = argv[0];
  if (argc > 1 && argv[1][0] == '-') {
  pagesize = atoi(&argv[1][1]);
  argc--;
  argv++;
  }
  if (argc == 1)
  print(stdin, pagesize);
  for (i = 1; i < argc; i++) {
  fp = efopen(argv[i], "r");
  print(fp, pagesize);
  fclose(fp);
  }
  exit(0);
 }

 print(fp, pagesize) /* print fp in pagesize chunks */
  FILE *fp;
  int pagesize;
 {
  static int lines = 0; /* number of lines so far */
  char buf[BUFSIZ];

  while (fgets(buf, sizeof buf, fp) != NULL)
  if (++lines < pagesize)
  fputs(buf, stdout);
  else {
  buf[strlen(buf)-1] = '\0';
  fputs(buf, stdout);
  fflush(stdout);
  ttyin;
  lines = 0;
  }
 }

 #include "ttyin2.c"
 #include "efopen.c"

3.8.40 p3.c

 /* p: print input in chunks (version 3) */